Sound insulation from tuning exaust inside cabin

[fedmax]

Hi all

I recently put a Tuning Exhaust from Tubistyle (Italy) on my 996 Turbo MJ 2002. The exhaust is ok from the outside, not too loud but I have a huge issue in the cabin: with low revs (1500-2500rpm) I get deep tone resonance inside the cabin to a level that is not fun to drive long distances. The exhaust is cool but I need to get rid of that resonance.

Does anyone of you have experience with sound insulation for the cabin? What material would you use and where would you place it? E.g. is there enough room underneath the carpets behind the back seats?

Any hints or links are helpful.

Thanks

Ronny

[Bostonduce]

You're fighting a losing battle.

The only thing that 100% doesn't give you a resonance/drone is the factory exhaust.

Virtually every type of aftermarket exhaust has been debated and discussed over and over. There are some that receive less drone complaints than others, but invariably, someone will say they hear it.

Most of the problem lies in the fact the engine is so close to the cabin compared to earlier (993tt) turbos. Plus, there is no giant intercooler over the engine which will absorb the sound energy.

BD

Edited March 17, 2010 by Bostonduce

[fedmax]

You're fighting a losing battle.

The only thing that 100% doesn't give you a resonance/drone is the factory exhaust.

Virtually every type of aftermarket exhaust has been debated and discussed over and over. There are some that receive less drone complaints than others, but invariably, someone will say they hear it.

Most of the problem lies in the fact the engine is so close to the cabin compared to earlier (993tt) turbos. Plus, there is no giant intercooler over the engine which will absorb the sound energy.

BD

I don't need to get rid of it completely just damp it a little. Do noise barrier and damper material not help in this case? I was thinking on putting some in the area behind the rear seats and below the rear window.

[Bostonduce]

I've used Dynamat (both foam and adhesive foil) in other vehicles, with limited success only because I was not willing to do the full monty and cover everything.

If you see a professional sound insullation job, the amount of material they use is depressingly large. Covers every inch of interior surface opposite the sound source.

Sound is a funny thing to try and quench. I've been told that if any little pathway remains, it will find a way in.

See my original post.

BD

[fedmax]

I did add some Alubutyl insultation about 2 weeks ago...little effect about 10% better. The good effect is that I do not hear the relays vibrating anymore. Anyway I'll take the exhaust off this Thursday, will do a performance tes with the driftbox to see how much power I loose.

[number9ine]

You're fighting a losing battle.

The only thing that 100% doesn't give you a resonance/drone is the factory exhaust.

Virtually every type of aftermarket exhaust has been debated and discussed over and over. There are some that receive less drone complaints than others, but invariably, someone will say they hear it.

Most of the problem lies in the fact the engine is so close to the cabin compared to earlier (993tt) turbos. Plus, there is no giant intercooler over the engine which will absorb the sound energy.

BD

I don't need to get rid of it completely just damp it a little. Do noise barrier and damper material not help in this case? I was thinking on putting some in the area behind the rear seats and below the rear window.

There's already a fair amount of sound insulation in those areas, especially for a sports car. Instead of tearing out your interior and installing Dynamat on everything I'd go back to OEM. Not to editorialize, but what sounds cool to you on-throttle in your cabin may disturb the rest of us outside, and at part throttle disturbs you. Seems like a lose-lose to me for an expensive part that doesn't realize any real power gain.

To each their own however. If you find a solution, please share.

Mark

[ALLSPEED]

There's already a fair amount of sound insulation in those areas, especially for a sports car. Instead of tearing out your interior and installing Dynamat on everything I'd go back to OEM. Not to editorialize, but what sounds cool to you on-throttle in your cabin may disturb the rest of us outside, and at part throttle disturbs you. Seems like a lose-lose to me for an expensive part that doesn't realize any real power gain.

To each their own however. If you find a solution, please share.

Mark

So what is reasonable gain? 1,2,3,5,7,10 percent or more?

[fedmax]

So what is reasonable gain? 1,2,3,5,7,10 percent or more?

Good question I don't know but maybe Mark does? However what I do know is that I can share some stats tomorrow about what changed. I'll do a run this evening with the tubi on and another one tomorrow and share the difference. Will be measured with the DriftBox which is fairly accurate.

[number9ine]

So what is reasonable gain? 1,2,3,5,7,10 percent or more?

Good question I don't know but maybe Mark does? However what I do know is that I can share some stats tomorrow about what changed. I'll do a run this evening with the tubi on and another one tomorrow and share the difference. Will be measured with the DriftBox which is fairly accurate.

A "reasonable gain" is highly subjective. I was expressing my opinion, and my statement on power gain is based on anecdotal evidence here and elsewhere about performance exhausts on these cars. Loren sums it up nicely in his blog post, Product claims and dynos -- and reality. I think we can agree that even the most optimistic mfr. claims of HP from an exhaust are relatively insignificant in a 400+hp car, and the implied guarantee of Porsche engineering is diminished by aftermarket kit. Isn't that one of the major reasons we buy these cars in the first place?

Again, just my opinion, but I find the idea of spending time and money to strip out the interior and install sound-deadening to be a waste when the problem can be solved by re-installing the stock exhaust. I guess it boils down to how much you love the sound and/or the look of your Tubi, since we lack sufficient data to measure its performance. I love the sound of a mean exhaust where it's functional--a racecar with straight pipes, for example--but adding sound for the sake of sound alone is of little value to me.

Please let us know if and how you eliminate your drone so others here can benefit.

Mark

Edited April 21, 2010 by number9ine

[fedmax]

Please let us know if and how you eliminate your drone so others here can benefit.

Mark

As stated previously I have an appointment to put the stock exhaust back on tomorrow so that will eliminate the drone. Other than that based on my experience (I added alubutyl to eliminate drone that doesn't work) there is no way.